Electronic instruments such as Digital Oscilloscopes and other test and measurement equipment typically have an array of control knobs and buttons for selecting functions and adjusting parameters. Some such instruments have multi-function knobs that perform different functions in different circumstances. This permits the use of larger screen sizes on instruments of a given size, with smaller control panels.
When a knob is to perform multiple functions, it is useful to provide some kind of indication to the user about the current function. This has typically been achieved with adjacent illuminated annunciator labels, such as with light sources behind light-transmissive icons or text in a film on the instrument's front panel. However, with the increasing number of functions, the front panel may appear cluttered, may have inadequate space, or there may be confusion as to which label applies to which knob.
Illuminated knobs have been used in some applications, primarily for identifying the location or setting of a knob in a dark environment such as an automotive or aircraft instrument panel. Such knobs are employed with special switches to allow illumination through passages or light pipes. However, for sophisticated applications requiring controls meeting demanding electronic specifications, such illumination is impractical because such controls are not designed to transmit the needed light. Illumination techniques for such controls would generally lead to an unattractive or non-uniform result.
While a custom rotary switch having certain optical properties or configuration may be designed, this is often impractical for many applications where only small quantities are required (unlike the automotive industry) and where there is cost sensitivity (unlike the aerospace industry.) Thus, there is a need for a system that operates in conjunction with off-the-shelf switches.
The preferred embodiment addresses these needs in the following: